Stihl 036 scored piston?

[Baby Grand]

In my previous thread I got some good advice about what bar & chain I should get for a donor 036.
I may have hitched the cart before the horse a bit. Tonight, I started checking the saw out.
First off, it really needs a new drive sprocket - that thing looks like it must have been throwing
the chain all the time.
I discovered that the plug was finger tight. So I removed the top and aft plastic covers.
The air filter was looking really choked with fine saw dust, so I did my best to lightly brush it off
with a stiff bristled brush.
Then I decided to remove the muffler/spark arrestor(?) - the boxy black stamped sheet metal
thing on the forward end, held on with 4 torx bolts. I got a bit of a shock when I saw the piston.
Both it and the rings look pretty well scored.
But I've never had a chainsaw apart, so I'm not sure if it's toast, or just showing normal wear & tear.
Here's what I saw:







Is it time for a rebuild? It sure doesn't feel very smooth when you pull the cord.
Should I get the NWP Piston and Cylinder Assembly (48mm) for Stihl 036 from Bailey's?
Thanks for all your ideas & helping the greenhorn!

-Jim

 

[s219]

Looks like the saw may have been run with straight gas (i.e., no oil mixed in). This is very common with chainsaws, unfortunately.

 

[art]

There sure is enough damage, and I wonder if the crank seals are good.

 

[medic1050]

When I burned out my 044 I found all the parts I needed to find at Bailey's Online. Check them out.

I melted the piston running the saw hot on the hottest day of last july. The piston and rings werre shot but I was able to clean up the cylinder with muriatic acid and Q tips. $5 at a saw shop got the cylinder reamed to re new the crosshatching and $50 for a new piston and rings had the saw was up and running again.

 

[LD1]

Its toast. But the real question is weather the cylinder is toast too or not?? The first pic shows the cylinder on the intake I think??? And that looks good. But the most wear is always the exhaust side. So... You can either take the jug off, or you can pull the carb off and look to the back side cylinder wall.

The condition of the cylinder makes all the difference. If it just needs a piston and ring, you are looking @ a $30-$50 repair if you do it yourself and thats for a good piston. If the cylinder is toast too......well....~$130-$150 gets an aftermarket kit, and north of $300 for OEM.

Taking the cylinder off is easy, especially since you already have the top-cover off, and muffler off. All thats left is the carb, and plug wire, and 4 bolts that bolt the jug down.

 

[Baby Grand]

Looks like the saw may have been run with straight gas (i.e., no oil mixed in). This is very common with chainsaws, unfortunately.

That was my impression, too.

 

[Baby Grand]

There sure is enough damage, and I wonder if the crank seals are good.

I think I'm about to find out ...

When I burned out my 044 I found all the parts I needed to find at Bailey's Online. Check them out.

I melted the piston running the saw hot on the hottest day of last july. The piston and rings werre shot but I was able to clean up the cylinder with muriatic acid and Q tips. $5 at a saw shop got the cylinder reamed to re new the crosshatching and $50 for a new piston and rings had the saw was up and running again.

That's good information - It looks like I'm doing a full disassembly now. I'll keep the muriatic trick in mind. I have had very good luck with Bailey's for other, tree related stuff, so that's usually the first place I go look, and usually where I buy.

 

[Baby Grand]

Its toast. But the real question is weather the cylinder is toast too or not?? The first pic shows the cylinder on the intake I think??? And that looks good. But the most wear is always the exhaust side. So... You can either take the jug off, or you can pull the carb off and look to the back side cylinder wall.

The condition of the cylinder makes all the difference. If it just needs a piston and ring, you are looking @ a $30-$50 repair if you do it yourself and thats for a good piston. If the cylinder is toast too......well....~$130-$150 gets an aftermarket kit, and north of $300 for OEM.

Taking the cylinder off is easy, especially since you already have the top-cover off, and muffler off. All thats left is the carb, and plug wire, and 4 bolts that bolt the jug down.

Thanks for the encouragement. I have to keep reminding myself this isn't a Swiss watch - everything seems very simple. I'll do a full tear down. Now I'm hoping the crank assembly didn't run dry for very long, too, so I want to see how it and it's bearings look. And the seals.

Hope it's salvageable. I'd really like to fit this with a .375 24" bar & chain for the odd big tree that needs dropping or cutting up for splitting.

This is actually kind of good - for all the many hours I've spent using saws, I've never serviced one, other than sharpening the chain or replacing the odd air filter or spark plug. It's an adventure!

-jim

 

[LD1]

Just remember that the piston will ONLY go in one way. Well...I should say it is only supposed to go together one way, because you "CAN" but it together backwards but you will probabally tear the ring out of it and trash the new piston and cylinder if you do. There is an arrow on the piston (or some kind of marking) read the instructions to find out wether it points toward the intake or exhaust. Reason for this ring placement. Saws have a pin in the ring land that prevent the ring from spinning and letting an end "pop" out and catch in the exhaust port. Because a 2-stroke ISNT a smooth bore, and it has ports in the cylinder, where the ends of the ring meet HAVE to stay on a smooth part.

Which brings me to my next point...Make sure you install the ring right.:thumbsup: So it wont rotate.

 

[Baby Grand]

Thanks for the heads-up on cylinder assembly. This is all new to me, so it's a huge help.

 

[LD1]

Wether it needs just a piston and rings, or a cylinder as well, its all pretty easy and straight forward. Its not often that the crank bearings and seals need done. They are pretty resilient.

Get it appart and get us some pics of the exhaust side of that cylinder:thumbsup:

 

[Baby Grand]

Getting it apart is becoming "interesting". I had to walk away from it last night. Too many biting bugs, not enough light and patience running low. Not a good recipe for doing it right. Will consult manuals before trying again.

 

[LD1]

Dont be afraid to ask questions and/or post pics of what you are having trouble with. For me, the absolute hardest thing is getting the little cir-clips out of the piston to take it off the rod. But that is after you already have the cylinder off.

It also helps to use an air-compressor and get everything CLEAN before taking off the jug. You dont want all that crud to fall down in the crankcase. And if you already have the carb off, make sure you either stick a rag in the intake or make sure the piston is blocking the port before you clean it with compressed air.

 

[xyz123]

Even though it looks straight gassed. I would still check the seals, rubber intake, etc for a source of air leaks. Check those bearings too, even though probably nothing wrong with them. Better safe then smoke another top end or piston.

I just redid a 036 pro and it's back at it. Good Luck.

 

[Baby Grand]

That fine sawdust/bar oil "mung" was part of my frustration the other night. I'll take the compressor to it before
I do any more tear down. I got hold of the repair manual, last night, and started to study it - $4.95 well spent!
It shows 4 bolts that are accessed through deep holes in the head, that I completely missed seeing in my initial
tear down attempt.

 

[Baby Grand]

Thanks for the tip, xyz123. I will definitely check the bearings and for air leaks. Since I don't know why the piston got scored in the first place, I'd like to eliminate as many possible causes before I try to fire it up again. Since I don't really need this saw I can take my time with it and wait for any parts I may need.

 

[LD1]

It shows 4 bolts that are accessed through deep holes in the head, that I completely missed seeing in my initial
tear down attempt.

Yep. I assumed you knew this. Those bolts are all that hold the cylinder (jug) on the crankcase. After the carb/intake and muffler is off, take those 4 bolts out and the cylinder just slides off the piston.

A couple of other notes:

1. Sometimes there is an anti-vibe mount that connects the cylinder to the handle. That needs removed as well.

2. You dont always need to remove the top-handle, but it makes things soooo much easier getting the jug off.

3. Most everything on saws is T27 torx. At least on the huskys and dolmars and few stihls I have worked on. You need a good one and not an el-chepo one for them 4 jug bolts because sometimes they are a PITA and really tight.

4. Final note, once you take the jug off, wether you decide to re-use or get a new one, look at the bottom of the cylinder and see if it is beveled. This helps on re-install so you dont snag the ring. If it is not, you can either bevel it, use a ring compressor, or just work it in with about 3 hands/fingers. But either way, if it isnt beveled (or beveled much) just be aware of it upon re-install.

 

[xyz123]

I got hold of the repair manual, last night, and started to study it - $4.95 well spent!

Should have ask, I could have gave you one free. I have a IPL and service manual request sub-forum on chainsawrepair.

 

[Baby Grand]

Should have ask, I could have gave you one free. I have a IPL and service manual request sub-forum on chainsawrepair.

I am so going to keep this in mind!

 

[Baby Grand]

Okay, got the jug off last night after some difficulty. The long series of holes through the fins on the jug/head were misaligned with the bolts and almost exactly the same diameter as my Stihl torx scrench - so the bit wouldn't engage the bolts. Typical, shoddy German engineering! Sorry, as an American engineer, I couldn't resist...
Had to open up the holes in 2 locations with an N sized drill to seat the bit:



Wear in the jug doesn't look as bad as I was anticipating. i was thinking about trying to remove the smeared aluminum using the muriatic acid trick, but saw a good sized pit/spall started on the exhaust side, down low (near the top of the photo, close to the chamfer & flange):







Piston & rings are toast:





Time for a new sprocket:



Clutch side looked oily & wet, so I'm going to give the seals a good looking at:



Once I get the clutch apart - more reading for me.
The crank bearings seem tight, turn smoothly and with little effort, so that was good news.
So far it looks like I'm getting a new sprocket & spark plug, a new jug & piston.
New impulse tube & fuel line.
What else would I be foolish not to replace, now that it's torn down?